Process for preparing color proofs

ABSTRACT

COLOR PROOFS, COLORED FACSIMILES OF A COLORED DESIGN WHICH IS TO BE PRINTED ON AN ARTICLE, ARE PREPARED BY EXPOSING A PHOTOGRAPHIC FILM HAVING A TRANSPARENT BASE TO AN IMAGE OF THE DESIGN. THE FILM IS DEVELOPED, BUT NOT FIXED, AND THEN CONTACTED WITH AN ETCHIG SOLUTION TO REMOVE THE EXPOSED AREAS OF THE EMULSION LAYER. THE ETCHED FILM IS THEN FIXED AND COLORING MATERIAL APPLIED THERETO, THE COLORING MATERIAL ADHERING TO THE NON-ETCHED (UNEXPOSED) AREAS OF THE EMULSION.

United States Patent 01 hoe 3,595,654 PROCESS FOR PREPARING COLOR PROOFS Stephen R. Hawley, West Chicago, and Bernard M.

Bartosch, Hoffman Estates, 111., assignors to Continental Can Company, Inc., New York, N.Y.

No Drawing. Filed May 29, 1968, Ser. No. 732,823

Int. Cl. G03c 5/00 U.S. Cl. 96-35 6 Claims ABSTRACT OF THE DISCLOSURE Color proofs, colored facsimiles of a colored design which is to be printed on an article, are prepared by exposing a photographic film having a transparent base to an image of the design. The film is developed, but not fixed, and then contacted with an etching solution to remove the exposed areas of the emulsion layer. The etched film is then fixed and coloring material applied thereto, the coloring material adhering to the non-etched (unexposed) areas of the emulsion.

BACKGROUND OF THE INVENTION (1) Field of invention The present invention relates to a method of forming a color image on a support and more particularly relates to a method of forming multi-color art work for use in proofing the same prior to the production of printing plates.

(2) The prior art Color proofs are principally used in the lithographic arts and are a colored facsimile of a colored printing or design which is to be lithographed or otherwise printed on an article, such as a package, can or other container. The color proof closely simulates the colored design to be used in the printing and acts as a guide for color balance and a means of checking register, correction of design and copy. Using color proofs, the user can more easily visualize the design which is to be printed on his product, as they have a very close appearance to the final printed design.

The prior art methods of preparing color proofs generally involve a tedious and expensive hand rendering of the colored design or print.

The present invention provides a rapid and effective method of preparing color proofs which compare closely with the press-run reproduction and eliminates a major portion of the hand labor required in preparing the color proofs.

SUMMARY OF THE INVENTION In accordance with the present invention, there is provided a method of preparing a color proof wherein an image is first printed onto the face of a light-sensitive silver halide emulsion coated on a transparent film base. The exposed portions of the film are developed and then dissolved by an etching solution to remove the developed areas of the film. The etched film is stabilized to make it nonsensitive to light. Selected coloring material is then applied to the stabilized film, the coloring material adhering to the non-etched portions of the film face.

PREFERRED EMBODIMENTS In preparing color proofs by the method of the present invention, a black and white reproduction drawing of the desired design is made. A photographic positive is made of the drawing by exposing the drawing on a photographic material composed of an inert support base of cellulose acetate, polyester (Mylar) or other transparent film materials having a suitable light-sensitive gelatinsilver halide emulsion coated on one face of the body.

Photographic materials which may be employed in the method of the present invention may be any of the regular emulsion-coated films manufactured by the several well-known manufacturers who supply film for use in the graphic arts. Examples of commercially available gelatin-silver halide coated film which can be employed in the method of the present invention include Cronar film, a polyester-based film available from E. I. du Pont de Nemours & Company, and Kodalith Film, a cellulose acetate-based film which carries a silver bromide emulsion, manufactured by the Eastman Company.

After exposure, the photographic positive is immersed in a developer solution in the ordinary manner. The developed film is then subjected to an etching solution for the purpose of removing the exposed silver and the gelatin of the emulsion in immediate contact with the exposed silver. The developed film is exposed to the etching solution for a time suificient to etch the film to the base in the exposed area of the film. A bleaching agent, such as H 0 is incorporated in the etching solution. These operations are carried out in the dark or in non-actinic light so that the film is not exposed to light.

An etching solution that has been found suitable to employ in the method of the present invention is a solution composed of 30 cc. of 4 percent hydrogen peroxide, 20 grams copper sulfate, 5 cc. concentrated nitric acid, and 0.5 gram potassium bromide dissolved in one liter of water. The developed film is exposed to the etching solution for aperiod of about 1 minute to about 3 minutes, whereby the exposed silver and the gelatin, in immediate contact with it, are disengaged or removed from the rest of the emulsion and taken up by the solution.

After etching, the photographic material is transferred to a stabilizing bath. If a clear image suitable for transparent coloring is desired, a suitable stabilizing bath is an acidic solution of ammonium or sodium thiosulphate. The primary function of this stabilizing bath is to convert the undeveloped silver halide to a soluble complex which can be washed out of the gelatin and stabilize the film.

If opaque color is desired, the photographic material is immersed in a stabilizing bath containing a solution of potassium iodide which will make the image impervious to light.

The fixed etched film is then colored by spreading suitable coloring agents in the areas of the image which are required to be colored, using different materials of different color where required. Coloring materials, such as water colors and dyes, when applied to the etched film will adhere to the non-etched, fixed gelatin-coated areas of the film. Superfluous coloring material may be washed or simply wiped clean with saliva or gum arabic solution applied to soft absorbent tissue from the etched areas which are inert and to which the coloring materials will not adhere.

Water colors marketed under the tradename Dr. Martins Water Colors have been found particularly suitable for use in the method of the present invention. After application of the coloring material, contrasting backgrounds for the print may be obtained by the use of colored background materials which are viewed through the transparent portions of the print. By preparing multiple copies of the design using the process of the present invention, and using coloring agents of different colors, a number of reproductions of the same design in different color combinations can be prepared.

What is claimed is:

l. A method of preparing a color proof which comprises exposing to an image the face of a film consisting of a light sensitive gelatin-silver halide emulsion coated on a transparent film base, developing but not fixing the film, chemically etching the film to remove the exposed 3 areas of the emulsion containing silver and the gelatin associated therewith, stabilizing the non-etched areas of the emulsion and then applying a coloring material to the etched, emulsion, the color material adhering only to the non-etched portions of the emulsion.

2. The method of claim 1 wherein the transparent film base is cellulose acetate film.

3. The method of claim 1 wherein the transparent film base is a polyester film.

4. The method of claim 1 wherein the etched film is stabilized with an acidic solution of ammonium thiosulfate to obtain a clear non-etched area.

5. The method of claim 1 wherein the etched film is stabilized with an acidic solution of sodium thiosulfate to obtain a clear non-etched area.

6. A method of preparing a color proof which comprises eXposing to an image the face of a light sensitive gelatin-silver halide emulsion coated on a transparent film base, developing but not fixing the film, chemically etching the film to remove the exposed areas of the emulsion containing silver and the gelatin associated therewith,

References Cited UNITED STATES PATENTS 1,067,198 7/1913 Sandig 83 1,807,809 6/1931 Tuttle 83 1,518,945 12/1924 Taylor 962 2,3 08,023 1/ 1943 Peterson 83 OTHER REFERENCES Flexichrome: Studio Light, July 1949, pp. 4, 6, 7, 9, 10.

Color Control From a Paintbrush; Eastman Kodak reprint from Commercial Camera Magazine, vol. 2, No. 4, August 1949, pp. 1-4.

J. TRAVIS BROWN, Primary Examiner J. WINKELMAN, Assistant Examiner 

